Preserve approved pixel tower prototype as development baseline

tests/performance/README.md

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+# PERF-MVP-001 acceptance harness
+
+This standalone harness composes the real World, Path, Facility, Guest, Staff,
+Inventory, Logistics, Event, Economy, and performance-budget services through
+their public APIs.
+
+The default command runs a smaller 24-hour smoke tier:
+
+```sh
+godot --headless --path . --script res://tests/performance/test_perf_mvp_001.gd
+```
+
+The opt-in command runs the exact PERF-MVP-001 fixture:
+
+```sh
+PERF_MVP_FULL=1 godot --headless --path . --script res://tests/performance/test_perf_mvp_001.gd
+```
+
+Exit status `0` means the selected tier passed, `1` means a validation or
+performance budget failed, and `2` means the requested fixture was incomplete.
+Every run prints a machine-readable `PERF_MVP_001_REPORT=<json>` line with exact
+fixture sizes, timings, backlog ages, validation results, and limitations.